1. Field of the Invention
This invention relates to a coaxial twin-rotor type helicopter in which upper and lower coaxial rotors are rotated in opposite directions. More particularly, this invention relates to a coaxial twin-rotor type helicopter having a compact, simple control mechanism. The invention also relates to a coaxial rotor type helicopter in which the rotors are covered by a protective frame.
2. Prior Art Description
Various helicopter structures are known. To realize a small, one-man helicopter that is easy to use, the present inventors are developing a coaxial twin-rotor type helicopter in which thrust and lift are obtained by counterrotating a lower and an upper rotor provided on the same axis. In a twin-rotor helicopter, torque is counteracted by having upper and lower rotors of the same shape rotate in opposite directions. As such a configuration eliminates the need for a tail rotor, and therefore enables the overall dimensions to be reduced, it is a suitable basic configuration for a small, one-man helicopter. The attitude and the direction of the helicopter are controlled basically by tilting the tips of the rotor blades with respect to the horizontal plane, and by controlling the attack angle of the rotor blades.
However, the control mechanisms of such conventional coaxial twin-rotor type helicopters are complex and require a large installation space, making them unsuitable for the type of small helicopter the present inventors are developing. Moreover, when this type of helicopter is used for tasks such as spraying agricultural chemicals, unlike a large helicopter, it is generally flown at a low altitude, and when operated at low altitude, it is usually used in hovering mode. This means there is a high possibility of people working on the ground being struck by the rotors. There is also a high likelihood of the rotors hitting and breaking electric power lines.
An object of this invention is therefore to provide a coaxial twin-rotor type helicopter having a compact, simple control mechanism.
Another object of the invention is to provide a coaxial twin-rotor type helicopter having a compact, simple yaw control mechanism.
Another object of the invention is to provide a safe coaxial twin-rotor type helicopter having rotors that do not hit people or electric power lines or the like.